ok, so maple is stiffer than mdf, but what about weight/mass ?
@twinter
where you find data sheet ?
should be very intresting
@twinter
where you find data sheet ?
should be very intresting
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natural grain boards will have >5:1 variation in stiffness depending on grain angle to bending axis
http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf
plywoods, particle board will have much more uniform properties
moisture content expansion/contraction is also a bigger problem in any assembly of natural boards with differing grain orientation across joints
composite construction with constrained layer damping and damping bracing seems to be the way to go for reduced loudspeaker cabinet radiation, lots of threads
http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf
plywoods, particle board will have much more uniform properties
moisture content expansion/contraction is also a bigger problem in any assembly of natural boards with differing grain orientation across joints
composite construction with constrained layer damping and damping bracing seems to be the way to go for reduced loudspeaker cabinet radiation, lots of threads
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Diypass, I've been collecting the data from different sources over a period of time. There's about a 10% variance depending on the source. I listed just a selection of a few relevant materials. If you want density data, I recommend Googling for the data. Sometimes one finds a table of applicable materials.
JCX, agree with your posting. What is the page in your link showing the stiffness relative to grain orientation for wood? I looked, but its a 500 page document, even attempted to used the index. If solid wood is used grain orientation and moisture content is very important. I have used MDF and Baltic Birch myself. MDF and Baltic Birch have very little internal damping, so effective efforts have to be made to control resonances. Even stiffening braces can act as resonance generators if one is not careful.
I believe there is promise for several of the tropical woods such as Ipe, which has a very high stiffness, around 3,500,000 psi modulus of elasticity (three times the stiffness of Baltic Birch Plywood and seven times that of MDF), and has high internal damping, maybe 4 times that of Baltic Birch Plywood or MDF. Even if only used for the front baffle or bracing. Most Ipe imported is air dried and used for higher grade decking. Some kiln dried Ipe is imported, which would be required for indoor use.
I will post more informative links later, when I have more time.
JCX, agree with your posting. What is the page in your link showing the stiffness relative to grain orientation for wood? I looked, but its a 500 page document, even attempted to used the index. If solid wood is used grain orientation and moisture content is very important. I have used MDF and Baltic Birch myself. MDF and Baltic Birch have very little internal damping, so effective efforts have to be made to control resonances. Even stiffening braces can act as resonance generators if one is not careful.
I believe there is promise for several of the tropical woods such as Ipe, which has a very high stiffness, around 3,500,000 psi modulus of elasticity (three times the stiffness of Baltic Birch Plywood and seven times that of MDF), and has high internal damping, maybe 4 times that of Baltic Birch Plywood or MDF. Even if only used for the front baffle or bracing. Most Ipe imported is air dried and used for higher grade decking. Some kiln dried Ipe is imported, which would be required for indoor use.
I will post more informative links later, when I have more time.
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Compiled from several of my posts on another website:
I am currently in the process of building a three way tower speaker, approximately 41" tall. After years of reading numerous comments about MDF and Baltic birch plywood, I built the cabinet walls of 1" MDF, with a 2" thick front baffle (2 layers). I used significant 3/4" Baltic birch plywood bracing. Applying the low tech knuckle rap test, the enclosure seemed to ring like a bell at numerous points (a little exaggeration here). I borrowed an accelerometer and a computer with FFT frequency spectrum analysis software (no CSD waterfall software), and found sharp resonances from 330 to 800 hertz. The Baltic Birch 4" x 8" internal braces were even resonating at 400 Hz, and they were attached on three sides. This matches what others have posted on the internet for MDF and plywood baffles using Cumulative Spectral Decay (CSD) plots.
I applied epoxy resin with fiberglass and carbon fiber woven roving, epoxy resin with powdered limestone, and extensional damping material to the interior walls. These were efforts to further stiffen and damp the enclosure walls, with some improvement noted though not as much as desired. A good learning experience. Next time will be different.
All three materials, HDF, MDF, and plywood (Baltic Birch) do not have significant internal damping, nor do natural stone materials. A damping factor of 0.1 (Q of 10) is consider good damping, with critical damping occurring with a damping factor of 2.0 (Q of 0.5). Another alternative, laminated bamboo appears to be stiffer and have greater internal damping, though be aware Ascend Audio mentioned concerns of warping with certain lamination configuration. Solid oak actually has greater internal damping than HDF, MDF, or plywood. Of course oak has the same concerns as all solid woods with grain orientation, and the resultant expansion & contraction with humidity changes.
From John Atkinson of Stereophile Magazine, Measuring Loudspeakers, Part 2, Page 7:
"However, looking at the behavior of the 300 or so loudspeakers that I have measured, several common factors emerge from the auditioning that correlate with the presence of strong cabinet resonances between 100Hz and 500Hz. (Remember that other "objective" factors will also contribute to the same subjective perceptions.) The clarity in the lower midrange can be disappointing. Tenor instruments like cello or trombone lack clarity or acquire a "woody" character. The bass can sound muddy, diffuse, one-note, blurred, or lacking in power, rather than tight, articulate, and extended, as it does in real life. Music can seem to drag, in rhythmic terms. Male voices can "boom" and female voices "hoot" at some frequencies and not others, with the result that the little inflections of tone that are characteristic of real voices become diluted. Centrally placed images, particularly of voices, can smear toward the speaker positions at some frequencies."
And from Stereophile:
http://www.stereophile.com/content/measuring-loudspeakers-part-two-page-6
Loudspeaker Cabinets, Panel Resonances, and Construction
A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration - Dagogo | A Unique Audiophile Experience
http://whitledgedesigns.com/uploads/CAE_part5_oct08.pdf
diyAudio.com Wiki - projects by fanatics, for fanatics
Sierra - The Cabinet
If you want to increase damping of the walls as some have proposed in good judgment, there are two basic ways (multiply layered systems will work also):
A) Constrained Layer Damping (CLD), 3 layer system
1. Stiff wall
2. Thin 2 to 4 millimeter adhesive elastic layer
3. Stiff wall
B) Extensional Damping, 2 layer system
1. Stiff wall
2. Thick visco-elastic layer, 1/2 to 1 times the thickness of the stiff wall and about
1/10 the elasticity of the stiff wall. The damping layer is attached with a stiff
adhesive. This layer should have a good internal damping factor
In general, constrained layer damping is more effective than extensional damping.
Articles on bracing:
http://www.audioholics.com/loudspea...echanical-noise-floor-in-speakers-pt-2-page-2
http://www.audioholics.com/loudspeaker-design/lowering-mechanical-noise-floor-in-speakers-pt-2
Vibration and Damping:
E-A-R Specialty Composites
Materials Internal Damping Test Data From Qualia Website, focus is for turntable plinths:
http://audioqualia.prophpbb.com/topic20.html
raw data - audio qualia 2
From the Qualia website, for extensional damping a 50/50 by weight mix of isophthalic polyester resin and bentonite (cat litter) has some promise for a damping layer, with a damping factor of 0.4.
I am currently in the process of building a three way tower speaker, approximately 41" tall. After years of reading numerous comments about MDF and Baltic birch plywood, I built the cabinet walls of 1" MDF, with a 2" thick front baffle (2 layers). I used significant 3/4" Baltic birch plywood bracing. Applying the low tech knuckle rap test, the enclosure seemed to ring like a bell at numerous points (a little exaggeration here). I borrowed an accelerometer and a computer with FFT frequency spectrum analysis software (no CSD waterfall software), and found sharp resonances from 330 to 800 hertz. The Baltic Birch 4" x 8" internal braces were even resonating at 400 Hz, and they were attached on three sides. This matches what others have posted on the internet for MDF and plywood baffles using Cumulative Spectral Decay (CSD) plots.
I applied epoxy resin with fiberglass and carbon fiber woven roving, epoxy resin with powdered limestone, and extensional damping material to the interior walls. These were efforts to further stiffen and damp the enclosure walls, with some improvement noted though not as much as desired. A good learning experience. Next time will be different.
All three materials, HDF, MDF, and plywood (Baltic Birch) do not have significant internal damping, nor do natural stone materials. A damping factor of 0.1 (Q of 10) is consider good damping, with critical damping occurring with a damping factor of 2.0 (Q of 0.5). Another alternative, laminated bamboo appears to be stiffer and have greater internal damping, though be aware Ascend Audio mentioned concerns of warping with certain lamination configuration. Solid oak actually has greater internal damping than HDF, MDF, or plywood. Of course oak has the same concerns as all solid woods with grain orientation, and the resultant expansion & contraction with humidity changes.
From John Atkinson of Stereophile Magazine, Measuring Loudspeakers, Part 2, Page 7:
"However, looking at the behavior of the 300 or so loudspeakers that I have measured, several common factors emerge from the auditioning that correlate with the presence of strong cabinet resonances between 100Hz and 500Hz. (Remember that other "objective" factors will also contribute to the same subjective perceptions.) The clarity in the lower midrange can be disappointing. Tenor instruments like cello or trombone lack clarity or acquire a "woody" character. The bass can sound muddy, diffuse, one-note, blurred, or lacking in power, rather than tight, articulate, and extended, as it does in real life. Music can seem to drag, in rhythmic terms. Male voices can "boom" and female voices "hoot" at some frequencies and not others, with the result that the little inflections of tone that are characteristic of real voices become diluted. Centrally placed images, particularly of voices, can smear toward the speaker positions at some frequencies."
And from Stereophile:
http://www.stereophile.com/content/measuring-loudspeakers-part-two-page-6
Loudspeaker Cabinets, Panel Resonances, and Construction
A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration - Dagogo | A Unique Audiophile Experience
http://whitledgedesigns.com/uploads/CAE_part5_oct08.pdf
diyAudio.com Wiki - projects by fanatics, for fanatics
Sierra - The Cabinet
If you want to increase damping of the walls as some have proposed in good judgment, there are two basic ways (multiply layered systems will work also):
A) Constrained Layer Damping (CLD), 3 layer system
1. Stiff wall
2. Thin 2 to 4 millimeter adhesive elastic layer
3. Stiff wall
B) Extensional Damping, 2 layer system
1. Stiff wall
2. Thick visco-elastic layer, 1/2 to 1 times the thickness of the stiff wall and about
1/10 the elasticity of the stiff wall. The damping layer is attached with a stiff
adhesive. This layer should have a good internal damping factor
In general, constrained layer damping is more effective than extensional damping.
Articles on bracing:
http://www.audioholics.com/loudspea...echanical-noise-floor-in-speakers-pt-2-page-2
http://www.audioholics.com/loudspeaker-design/lowering-mechanical-noise-floor-in-speakers-pt-2
Vibration and Damping:
E-A-R Specialty Composites
Materials Internal Damping Test Data From Qualia Website, focus is for turntable plinths:
http://audioqualia.prophpbb.com/topic20.html
raw data - audio qualia 2
From the Qualia website, for extensional damping a 50/50 by weight mix of isophthalic polyester resin and bentonite (cat litter) has some promise for a damping layer, with a damping factor of 0.4.
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A few more articles on enclosure baffle construction:
Loudspeaker Cabinet Bracing: A Detailed Look on Do's and Dont's | Audioholics
Myths & Facts about Loudspeaker Cabinets: Identifying Legitimately High Fidelity Designs | Audioholics
MDF and Baltic Birch Plywood are adequate materials for good enclosure construction, they just are not optimum.
Loudspeaker Cabinet Bracing: A Detailed Look on Do's and Dont's | Audioholics
Myths & Facts about Loudspeaker Cabinets: Identifying Legitimately High Fidelity Designs | Audioholics
MDF and Baltic Birch Plywood are adequate materials for good enclosure construction, they just are not optimum.
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twinter, you and I have been on the same research quest. That's an outstanding summary of the relevant links. Well done.
If anyone is into the math and wants to try calculating panel resonant frequencies using the plate theory equation in this link:
diyAudio.com Wiki - projects by fanatics, for fanatics
be aware that the equation has been transcribed incorrectly - there are too many variables included in the squareroot function. The correct equation is this:
f = (pi/ 2) * SQRT{D/ p} * [(1/a^2) + (1/ b^2)]
This methodology, A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration - Dagogo | A Unique Audiophile Experience, strikes me as well researched and fact-based and with certain variations, more easily accessible to diy'ers than some other methods out there.
If anyone is into the math and wants to try calculating panel resonant frequencies using the plate theory equation in this link:
diyAudio.com Wiki - projects by fanatics, for fanatics
be aware that the equation has been transcribed incorrectly - there are too many variables included in the squareroot function. The correct equation is this:
f = (pi/ 2) * SQRT{D/ p} * [(1/a^2) + (1/ b^2)]
This methodology, A Whitepaper: The Audibility Of Cabinet Panel Resonances and Pat. Pend. Method Of Reduction Of Audible Coloration - Dagogo | A Unique Audiophile Experience, strikes me as well researched and fact-based and with certain variations, more easily accessible to diy'ers than some other methods out there.
hey guys,
I looked at the website:
raw data - audio qualia 2
seems incorrect to me some data:
as is possible that the MDF has a damping factor of 0.017 and the chipboard of 0.101?
in don't understand
the mdf is harder then chipboard so must be an highter damping factor
please explain be this
I looked at the website:
raw data - audio qualia 2
seems incorrect to me some data:
as is possible that the MDF has a damping factor of 0.017 and the chipboard of 0.101?
in don't understand
the mdf is harder then chipboard so must be an highter damping factor
please explain be this
One aspect I've seen little on is jointery and how the bending moments of one panel are induced into adjoining panels. By minimizing contact through use of chamfering the outer edge and it's mounting groove near the edge of adjoining panels. Flexation of one does not transfer into another. This joint uses a dampening layer which adds to the reduction of coupled energy.
A common method of incorporating this is the "box within a box", with the internal box constructed in this manner.
This loosely coupled wall combined with CLD of the box within a box is a spin on Harbeth technique.
Suggest CLD cross bracing of panels in the same manner. Bracing of a panels along the greatest dimension. Bracing of motors should be done cld, but to the corners instead of the side panel bracing as is typically employed.
Have explored these and just about every type construction imaginable over the last 40 years. Having a background in aeronautical engineering found many of these techniques in use where weight is the enemy. Building as such seriously adds to construction complexity, but could not possibly build without as it is as integral to the sound as the driver itself. An added plus is my back is thankful 🙂
A common method of incorporating this is the "box within a box", with the internal box constructed in this manner.
This loosely coupled wall combined with CLD of the box within a box is a spin on Harbeth technique.
Suggest CLD cross bracing of panels in the same manner. Bracing of a panels along the greatest dimension. Bracing of motors should be done cld, but to the corners instead of the side panel bracing as is typically employed.
Have explored these and just about every type construction imaginable over the last 40 years. Having a background in aeronautical engineering found many of these techniques in use where weight is the enemy. Building as such seriously adds to construction complexity, but could not possibly build without as it is as integral to the sound as the driver itself. An added plus is my back is thankful 🙂
Hardness has ZERO to do with damping factor..... damping down to internal 'structure' of the 'material'.
And if you really want to make it hard for the panel resonance's to take hold, brace on 'unequal' length diagonals, you can find example of this in some of Planet10's 'Spawn Horns' (OR Big Vent Reflex speakers - to be pernickity), though you'll have to ask them for the plan of 'Half Chilli Chang'.
And if you really want to make it hard for the panel resonance's to take hold, brace on 'unequal' length diagonals, you can find example of this in some of Planet10's 'Spawn Horns' (OR Big Vent Reflex speakers - to be pernickity), though you'll have to ask them for the plan of 'Half Chilli Chang'.
Hardness and damping factor are two very different parameters. Hardness is the resistance to indentation or scratching. Damping factor is the internal dissipation of energy in a material subject to vibrational excitation. A material with high damping factor tends to dissipate vibrational energy internally and does not have a sharp resonant frequency.
Glass is a very hard material that has a low damping factor and that will literally ring when excited by a moistened finger swirled around the edge and shatter if excited at its resonant frequency for a sustained period of time. Tar or pitch is a very soft material with a high damping factor.
Glass is a very hard material that has a low damping factor and that will literally ring when excited by a moistened finger swirled around the edge and shatter if excited at its resonant frequency for a sustained period of time. Tar or pitch is a very soft material with a high damping factor.
jReave, thanks for the comments. Please provide any other informative links that you may have.
Greebster, yes panel vibration reduction can be often be achieved though completely different and novel means. Does your a aeronautical engineering background help with structural vibrations and damping?
Diypass, as the above guys have stated, hardness is not one the major direct properties of vibration. The major properties are stiffness, mass, and damping.
Greebster, yes panel vibration reduction can be often be achieved though completely different and novel means. Does your a aeronautical engineering background help with structural vibrations and damping?
Diypass, as the above guys have stated, hardness is not one the major direct properties of vibration. The major properties are stiffness, mass, and damping.
Good plywood like Baltic Birch is hard to find :/ (for me anyways). I went to maybe 3 lumber yards, only to have the guys there look at me like I have six heads.
I would go with MDF for availability and density. It is very heavy and soft, meaning that it will absorb sound better rather than continue to resonate.
That's what I think anyways.
I would go with MDF for availability and density. It is very heavy and soft, meaning that it will absorb sound better rather than continue to resonate.
That's what I think anyways.
I haven't looked up the damping factors for MDF or chipboard (is this particle board, OSB or something else as you define it?), but their properties will be substantially dependent on the properties of the cured adhesives that bond the wood particles together. These composite wood materials do not lend themselves to the seat of the pants analysis that you seem to be applying.
Oh and don't expect to find quality BB plywood at the local lumberyard. Look for specialty plywood retailers who supply cabinetmakers.
Oh and don't expect to find quality BB plywood at the local lumberyard. Look for specialty plywood retailers who supply cabinetmakers.
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kevinahcc20,
I believe particle board is chipboard.
OSB:Oriented strand board - Wikipedia, the free encyclopedia
I've seen said that OSB is / could be a 'halfway house' between MDF and 'Plywood' in terms of internal damping / 'strength' - would be a devil to finish as 'natural surface is quite uneven.
After hunting all over my county and eventually finding a single place that sells Baltic Birch ply - A boat building materials specialist - I got very scared of the price.
They told me that there is are several types of WBP Plywood, comes in 5 / 7 / 9 / 11 veneer structures, thickness not withstanding.
My landlord decided to renovate the 'up stairs' flats balconies and the ply he bought - 9 layer WBP from a building material suppliers thats less than 4 miles from my doorstep.
I watched landlord chop this stuff to size and it has Very few voids and including the dreaded VAT, costs £35 per 8ft x 4ft sheet
BB is 3.3 times that excluding VAT.
Pays to scout about 😉
I believe particle board is chipboard.
OSB:Oriented strand board - Wikipedia, the free encyclopedia
I've seen said that OSB is / could be a 'halfway house' between MDF and 'Plywood' in terms of internal damping / 'strength' - would be a devil to finish as 'natural surface is quite uneven.
After hunting all over my county and eventually finding a single place that sells Baltic Birch ply - A boat building materials specialist - I got very scared of the price.
They told me that there is are several types of WBP Plywood, comes in 5 / 7 / 9 / 11 veneer structures, thickness not withstanding.
My landlord decided to renovate the 'up stairs' flats balconies and the ply he bought - 9 layer WBP from a building material suppliers thats less than 4 miles from my doorstep.
I watched landlord chop this stuff to size and it has Very few voids and including the dreaded VAT, costs £35 per 8ft x 4ft sheet
BB is 3.3 times that excluding VAT.
Pays to scout about 😉
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That's just me analyzing the material compared to some other woods which are (edit) "long natural fibers". Maybe I am not explaining myself as good but here are a few better explanations. (also I shouldn't say it's soft, but I mean more of brittle maybe, if you drop it you can break off a corner or can put deep scratches easily)
Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure.
And here is a good place which explains a lot
MDF Board FAQ - Tutorial
Look at the table in the mid page.
Q: What properties does MDF exhibit?
A: MDF has many qualities that make it an ideal replacement for plywood or particle board. It is dense, flat, stiff, has no knots and is easily machined. Its fine particles provide dimensional stability without a predominant "grain" (as is the case with lumber). Unlike most plywoods, MDF contains no voids, and will deliver sharp edges with no tearout. MDF is very well damped acoustically thus making it an ideal material for speaker enclosures.
Below are some metrics for MDF and other types of wood. Ex: Weight of MDF board. As you can see, MDF is very dense and heavy, but is not as stiff as other types of wood which is why bracing is suggested.
Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure.
And here is a good place which explains a lot
MDF Board FAQ - Tutorial
Look at the table in the mid page.
Q: What properties does MDF exhibit?
A: MDF has many qualities that make it an ideal replacement for plywood or particle board. It is dense, flat, stiff, has no knots and is easily machined. Its fine particles provide dimensional stability without a predominant "grain" (as is the case with lumber). Unlike most plywoods, MDF contains no voids, and will deliver sharp edges with no tearout. MDF is very well damped acoustically thus making it an ideal material for speaker enclosures.
Below are some metrics for MDF and other types of wood. Ex: Weight of MDF board. As you can see, MDF is very dense and heavy, but is not as stiff as other types of wood which is why bracing is suggested.
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